>Let’s start with the obvious: the only people having this conversation about iMessage are Americans
That makes it important. A large section of 300 million of the richest people on the planet want blue text bubbles rather than green ones, and will buy the expensive phone to get it. Fortunes have been made on much less.
Even more important is almost all of iPhones market share is in USA. So would apple care about maintaining the market where most of it's phones are sold? Well, ya, of course.
Apple has >1billion active units worldwide, or one for every three and a half people on the internet. While the USA market is highly profitable their operational scope is much larger.
That makes it important. A large section of 300 million of the richest people on the planet want blue text bubbles rather than green ones, and will buy the expensive phone to get it. Fortunes have been made on much less.